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Steady-State and Transient Behavior of Knotted Chains in Extensional Fields.
Vivek Narsimhan1, Alexander R Klotz2, Patrick S Doyle2
1Department of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States.
ACS Macro Letters
|June 2, 2022
Summary
Knots in polymers alter their dynamics in extensional fields, shifting extension curves to higher strain rates. Knot untying causes significant, transient changes in polymer chain extension and conformation.
Area of Science:
- Polymer Physics
- Soft Matter Physics
- Computational Biophysics
Background:
- Understanding polymer dynamics under external fields is crucial.
- Molecular topology, specifically knots, is increasingly recognized as a key factor influencing polymer behavior.
Purpose of the Study:
- To investigate the effect of molecular topology (knots) on the nonequilibrium dynamics of polymers.
- To analyze polymer evolution in planar extensional fields using simulations and experiments.
Main Methods:
- Brownian dynamics simulations were employed to model polymer behavior.
- Single-molecule experiments were conducted to validate simulation findings.
Main Results:
- Knotted polymers exhibit shifted extension versus strain-rate curves towards higher strain rates.
- Knot untying leads to substantial, temporary alterations in polymer chain extension.
- Complex topologies result in diverse time-dependent conformations during knot untying.
Conclusions:
- Molecular topology significantly impacts polymer nonequilibrium dynamics.
- Knots influence polymer response to extensional flow, consistent with Rouse-like theories.
- Knot untying is a dynamic process that introduces transient conformational changes in polymers.
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